We investigate Lagrangian transport on the surface of the ocean using a submesoscale permitting simulation of the Gulf of Mexico based on the Navy Coastal Ocean Model (NCOM). We find that simulated surface velocities and velocities inferred geostrophically from simulated sea surface height sustain Lagrangian transport with very similar characteristics. Our findings follow from the analysis of Lagrangian coherent structures and the statistics of separations produced by synthetic trajectory pairs, which show consitency with those produced by drifter trajectory pairs from the Grand LAgrangian Deployment (GLAD). Implications for high-resolution altimetry are discussed. Work supported by the BP/Gulf of Mexico Research Initiative.